1. Field of the Invention
This invention relates to an improved straddle type all terrain vehicle (ATV) and more particularly to the structure, placement and orientation of an air intake within the ATV.
2. Description of Related Art
FIG. 1A shows a related art ATV 700 including a frame 702, a pair of front wheels 704, and a pair of rear wheels 706. The frame 702 has mounted thereto a body 708, which is shown to include front facie 710 and rear fenders 712. Additionally, the ATV 700 includes a fuel tank 714 mounted thereto.
For the ATV 700 shown in FIG. 1A, the rear wheels 706 are supplied power from an engine 718. The engine 718 generates power by combusting a mixture of fuel and air. The fuel is delivered to the engine 718 from the fuel tank 714 by a suitable means, such as a fuel pump. Air is pulled from the atmosphere through an air intake system, indicated at 720, mixed with the fuel in a carburetor 743, and combusted within a chamber of the engine 718. An inlet 722 of air intake system 720 is positioned between the seat 710 and fuel tank 714. Accordingly, the inlet 722 is protected from debris and water entering therethrough.
FIG. 1B shows a schematic view of the air intake system 720 and engine 718. As shown, the air intake system 720 includes a pair of intake tubes 730, which on one end thereof provide the inlet 722, and are connected to a noise suppressing enclosure or silencer 732. The silencer 732 is a substantially voluminous enclosure, which serves to attenuate intake roar of the engine 718. The silencer 732 includes a hollow molded body 734 with an upwardly facing opening 736. A closure member (e.g., lid) 738 is detachably mounted (such as with clips 739) to the body 734 thereby sealing the opening 736. It is noted that the sealing of the opening 736 may be facilitated by a pliable sealing member 740 disposed between the body 734 and closure member 738. The silencer 732 is also connected to an intake duct 742, which is connected at an opposite end to the carburetor 743. As shown, an air filter 744 is disposed within the silencer 732 and may be connected to the end of duct 742 to filter or otherwise separate particulates through the air flowing from the air intake system 720 prior to delivery to the carburetor 743. As shown in FIG. 1A, the silencer 732 is positioned just behind the engine 718. The intake tubes 730 extend from the silencer 732, along an upper portion of the engine 718, to the position between the fuel tank 714 and the seat 710.
The main drawback of the air intake system 720 shown in FIGS. 1A and 1B, stems from the proximate positioning of the air intake 720 relative to the engine 718. In particular, the silencer 732 is positioned rearwardly of the engine 718 and adjacent thereto. Additionally, the intake tubes 730 are positioned above the engine 718, between the engine 718 and the seat 710, as is conventional. As such, the intake tubes 730 and silencer 732 are exposed to a substantial amount of heat generated by the engine 718, which serves to raise the temperature of intake air prior to combustion. Relatively high temperature intake air disadvantageously reduces engine efficiency and power output.
FIG. 2A is a perspective view showing a related prior art ATV 100 described in application Ser. No. 09/057,652 incorporated by reference into the provisional application No. 60/229,027 referenced above. The ATV 100 includes a pair of front wheels 102 and a pair of rear wheels 103. The front wheels 102 are covered by front fenders 117 and the rear wheels 103 are covered by rear fenders 116. A front rack 105 is provided above the front fenders 117 and the rack 106 is provided above the rear fenders 116. A pair of apertures or ventilation openings 120, provided in the rear fenders 116, supply intake air to a radiator and fan assembly 170 (FIG. 2B), which is generally beneath a seat 107. A pair of handle bars 110 is used to steer the ATV 100.
FIG. 2B is a top plan view of the ATV 100 shown in FIG. 2A, with the seat 107 being removed and the front and rear fenders 116, 117 being shown in phantom. The front and rear wheels 102 and 103 are supported by a main frame 121, while a subframe 122, which is connected to the main frame 121 through joints 124, supports the radiator and fan assembly 170. A suitable type of power unit, e.g., an engine 150, is preferably capable of simultaneously driving the front and rear wheels 102 and 103 through a suitable transmission, although rear wheel drive only ATVs are also contemplated. The ATV 100 also includes a carburetor 152, an exhaust pipe 154, a muffler 156, and an air intake system 200, which is shown in greater detail in FIG. 3.
FIG. 3 is a schematic view illustrating an intake air system 200. An inlet end 212 of a front air intake pipe 214 is positioned at the front of the ATV 100 adjacent the steering column, just below a mounting plate 115 for mounting equipment, e.g., an instrument panel and/or a dash board. The inlet end 212 is positioned at substantially the highest point of the ATV 100 to substantially eliminate entry of mud or water caused either by immersion when traversing relatively deep water or by splashing when traversing wet terrain. The front air intake pipe 214 is connected to a sleeve 216 and a rear air intake pipe 217 that leads to the air box 201, which is positioned just below a rear portion of the seat 107. Clamps 210 secure the front air intake pipe 214 to the sleeve 216, and the sleeve 216 to the rear air intake pipe 217. Intake air from the air box 201 is supplied to the carburetor 152 using a hose 206 that is held by a clamp 210 to the carburetor 152. Air is supplied to an engine valve cover (not shown) and the engine 150 using a vent hose 222, clamps 218 and 219, PCV valve 221, oetiker clamp 227, vent hose 226, “Y” fitting 228, hoses 229 and 230 and fitting 233. The air filter 155 is placed in the air box 201 along with a foam member 220. Air intake tubes 211 fit within the air filter 155. A cover 226 is secured by cover brackets 232 to the air intake box 201.
The related art air intake system 200 suffers from at least two main drawbacks. The first main drawback is that the cumulative length of the air intake pipes 214, 216 and 217 may create vibration and sound resonance that affects the fuel-to-air air ratio in the carburetor 152. Vibration and sound resonance adversely affect air pressure in the carburetor 152, thereby causing fuel-to-air to ratio to be either lean or rich, therefore adversely affecting performance of the engine.
The second main drawback to the related art intake system 200 is schematically illustrated in FIG. 4. In some circumstances, the ATV 100 is used in conditions where it is necessary to cross bodies of water, such as rivers and streams. It is for this reason that the inlet end 212 of the front end intake pipe 214 is positioned at the highest point of the ATV 100, near the steering column and just below the mounting plate 115, as discussed previously. However, when the ATV 100 is crossing a deep stream having a predetermined depth Dnominal, a wall of water or wave W having a depth Dmax greater than the predetermined depth Dnominal is created and travels upwardly against the front of the ATV 100. This phenomenon can introduce water into the inlet end 212 of the front air intake pipe 214, which is undesirable. Typically, the wave W dissipates just rearward of the front wheels 102, and the depth Dwake of the water behind the wave W is less than the predetermined depth Dnominal of the water because of the wake created by the ATV 100.
Furthermore, both of the prior art intake systems 200 and 720 share an additional drawback in that the respective inlets 212, 722 are located just in front of the rider. With this arrangement, the rider is exposed to a substantial degree of noise and vibration emanating from the inlets 212, 722.